Reuters is reporting that the Beirut port explosion was preceded by a series of blasts, the last of which was a combustion of fireworks that apparently set off a warehouse full of ammonium nitrate, an seismological and munitions expert said on Thursday noting that six of the blasts ahead of the main explosion were spaced at 11-second intervals.
Boaz Hayoun of Israel’s Tamar Group and a former Israeli military engineering officer whose current roles include overseeing safety standards for explosives use in Israel, said the six preliminary blasts were tracked by a seismological sensor array installed some 70 km (43 miles) off Lebanon’s coast by the international geological project IRIS.
“I cannot say categorically what caused this, but I can say these blasts were at the same location,” Hayoun told Reuters.
Hayoun told Reuters the first five blasts, each of a magnitude consistent with several tonnes of explosives going off, may have taken place underground and gone unheard by Beirut witnesses.
Another indication of underground explosions, he said, was the 43-meter (yard) depth of the crater left at the port, which, he argued, could not have been created by the explosion of the amount of ammonium nitrate reported by Lebanese authorities.
“It would have been shallower, maximum 25 or 30 meters,” Hayoun said.
The sixth blast, he said, was larger than the previous five and consistent with a fire observed near the ammonium nitrate warehouse. Television footage of that fire, Hayoun said, left him convinced that it was “unequivocally” caused by the combustion of fireworks – and that this would have been sufficient to set off the ammonium nitrate in turn.